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This morning I found that I cannot change the brightness of my Dell XPs 13 laptop's display anymore. I tried the following to change the brightness

  • Use keyboard brightness keys
  • Run the commands shown below
  • Boot with kernel option acpi_backlight=vendor. This resulted in a dell_something folder being present in the /sys/class/backlight folder. Changing the brightness file in that folder does not help.
  • Add 'intel_backlight' to xorg.conf
  • Set "load legacy option ROM" BIOS option to enabled and "secure boot" to disabled
  • Boot with kernel option i915.disable-pch_pwm=0
  • Boot from a fresh Ubuntu 12.04 USB stick installation. I can still not control the brightness. This is strange as the laptop came preinstalled with 12.04. Maybe this a hardware problem?
  • Install latest intel video driver

Any ideas why this broke suddendly? I've upgraded from 12.04 to 14.04 in April and till yesterday the brightness keys were working fine.

Thanks!

echo 100 > /sys/class/backlight/intel_backlight/brightness
echo 100 > /sys/class/backlight/acpi_video0/brightness
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I used some help from this blog: itsfoss.com/fix-brightness-ubuntu-1310 It worked on a dell. Not able to run it on an acer.Hope it works for you –  user3058470 Jun 4 at 10:58
    
Thanks for your help. I found that article myself but I figured that solve the problem. The changes in the xorg.conf just make the brightness buttons work by echoing the appropriate value in thebrightness file. My problem, however, is that even when I manually changethe value the brightness does not changed. –  Lespaul86 Jun 4 at 13:09

3 Answers 3

For me, solution listed here helps - https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1249219/comments/30

Basically it works creating the /usr/share/X11/xorg.conf.d/20-intel.conf file with the following lines:

Section "Device"
        Identifier "card0"
        Driver "intel"
        Option "Backlight" "intel_backlight"
        BusID "PCI:0:2:0"
EndSection
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I got a fix for my dell 5521 laptop,

working for ubuntu 14.04 but will work for kernels v3.13+

sudo nano /etc/default/grub

change line

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" to 

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video.use_native_backlight=1"

then save and exit and run

sudo update-grub

then reboot

explanation is that acpi adds its own backlight control even if one is already present which is intel_backlight, adding this line forces acpi to use the intel backlight.

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This worked for my eeepc seashell series: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux" from http://ubuntuforums.org/showthread.php?t=1412922 and they got it from http://wiki.debian.org/DebianEeePC/Model/1005pe

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While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. –  KasiyA Nov 19 at 4:41

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